"Energy conservationist" Hotaro Oreki joins the Classic Lit Club at his high school at his sister's behest, to keep it from being shut down. Also joining the club are his best friend, Satoshi Fukube, and Eru Chitanda, a curious girl who enjoys mysteries.

Eru grows bored of the club's lack of activities, and suggests that they prepare an anthology to submit for the school's culture festival in the fall. While tracking down previous anthologies, the club discovers a mystery in the school's library.

Hotaro is torn between continuing with his "gray" life and the "rosy" life that the others live. A phone call from Hotaro's sister leads him to believe that there are pieces missing to his theory regarding the events of Sekitani's expulsion.

In search of a conclusion to their movie, the assistant director, the prop master, and the publicist meet with the Classic Lit Club members one at a time to propose their solutions to the unfinished murder mystery.

After meeting with Irisu, Hotaro has a change of heart, and sets his mind to solving the murder mystery. Hotaro and Satoshi discuss the nature of their own potential, and what each of them might be able to accomplish.

Eru's curiosity is drawn by the rash of thefts from the various clubs, and when Hotaro discovers a pattern to the crimes, Satoshi comes up with a way to publicize the Classic Lit Club through the school newspaper so they can sell their anthologies.

Eru appears on a school radio show, asking all the other students to stand with the Classic Lit Club against the phantom thief. Hotaro confronts the person he believes to be Jumoji. Satoshi comes to terms with his expectations.

Hotaro is enlisted by Eru to appear in a Dolls' Festival parade that her local shrine holds every year. When construction work unexpectedly causes a last-minute detour, it leaves the participants wondering what went awry.